Personal computer
personal computer; a desktop personal computer's CRT monitor, keyboard, and mouse are visible in the background.]] A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. PCs are intended to be operated directly by an end user, rather than by a computer expert or technician. Computer time-sharing models that were typically used with larger, more expensive minicomputer and mainframe systems, to enable them be used by many people at the same time, are not used with PCs. Early computer owners in the 1960s, invariably institutional or corporate, had to write their own programs to do any useful work with the machines. In the 2010s, personal computer users have access to a wide range of commercial software, free software ("freeware") and free and open-source software, which are provided in ready-to-run form. Software for personal computers is typically developed and distributed independently from the hardware or OS manufacturers. Many personal computer users no longer need to write their own programs to make any use of a personal computer, although end-user programming is still feasible. This contrasts with mobile systems, where software is often only available through a manufacturer-supported channel, and end-user program development may be discouraged by lack of support by the manufacturer. Since the early 1990s, Microsoft operating systems and Intel hardware have dominated much of the personal computer market, first with MS-DOS and then with Windows. Alternatives to Microsoft's Windows operating systems occupy a minority share of the industry. These include Apple's macOS and free open-source Unix-like operating systems such as Linux. Advanced Micro Devices (AMD) provides the main alternative to Intel's processors. Terminology "PC" is an initialism for "personal computer". The IBM Personal Computer incorporated the designation in its model name, but IBM has not used this brand for many years. It is sometimes useful, especially in a marketing context, to distinguish personal computers of the "IBM Personal Computer" family from personal computers made by other manufacturers. For example, "PC" is used in contrast with "Mac", an Apple Macintosh computer. This sense of the word is used in the "Get a Mac" advertisement campaign that ran between 2006 and 2009, as well as its rival, I'm a PC campaign, that appeared in 2008. Since none of these Apple products were mainframes or time-sharing systems, they were all "personal computers" and not "PC" (brand) computers History in 1983 (at American Museum of Science and Energy), an early example of a personal computer]] }} In the history of computing there were many examples of computers designed to be used by one person, as opposed to terminals connected to mainframe computers. It took a while for computers to be developed that meet the modern definition of a "personal computers", one that is designed for one person, is easy to use, and is cheap enough for an individual to buy.Roy A. Allan, A Bibliography of the Personal Computer resource: the Books and Periodical Articles, Allan Publishing - 2006, p. 73 Using the narrow definition of "operated by one person", the first personal computer was the ENIAC which became operational in 1946.Gene Carter, Wow! What a Ride!: A Quick Trip Through Early Semiconductor and Personal Computer Development, Lulu Press - 2016, chapter 8 It did not meet further definitions of affordable or easy to use. The Bendix G15 of 1956 was intended for use without an operating staff, and several hundred were made; it was too costly to be personally owned, however. An example of an early single-user computer was the LGP-30, created in 1956 by Stan Frankel and used for science and engineering as well as basic data processing.Link text, It was considered a bargain, selling for about $50,000. It came with a retail price of $46,000 equivalent to about $ ,000 today. Introduced at the 1965 New York Worlds Fair, the Programma 101 was a printing programmable calculator described in advertisements as a "desktop computer". It was manufactured by the Italian company Olivetti, and invented by the Italian engineer Pier Giorgio Perotto, inventor of the magnetic card system for program storage. The Soviet MIR series of computers was developed from 1965 to 1969 in a group headed by Victor Glushkov. It was designed as a relatively small-scale computer for use in engineering and scientific applications, and contained a hardware implementation of a high-level programming language. Another innovative feature for that time was the user interface combining a keyboard with a monitor and light pen for correcting texts and drawing on screen. In what was later to be called the Mother of All Demos, SRI researcher Douglas Engelbart in 1968 gave a preview of what would become the staples of daily working life in the 21st century: e-mail, hypertext, word processing, video conferencing, and the mouse. The demonstration required technical support staff and a mainframe time-sharing computer that were far too costly for individual business use at the time. By the early 1970s, people in academic or research institutions had the opportunity for single-person use of a computer system in interactive mode for extended durations, although these systems would still have been too expensive to be owned by a single person. Early personal computers generally called microcomputers were often sold in a kit form and in limited volumes, and were of interest mostly to hobbyists and technicians. Minimal programming was done with toggle switches to enter instructions, and output was provided by front panel lamps. Practical use required adding peripherals such as keyboards, computer displays, disk drives, and printers. Micral N was the earliest commercial, non-kit microcomputer based on a microprocessor, the Intel 8008. It was built starting in 1972, and few hundred units were sold. This had been preceded by the Datapoint 2200 in 1970, for which the Intel 8008 had been commissioned, though not accepted for use. The CPU design implemented in the Datapoint 2200 became the basis for x86 architecture used in the original IBM PC and its descendants. In 1973, the IBM Los Gatos Scientific Center developed a portable computer prototype called SCAMP (Special Computer APL Machine Portable) based on the IBM PALM processor with a Philips compact cassette drive, small CRT, and full function keyboard. SCAMP emulated an IBM 1130 minicomputer in order to run APL\1130. In 1973, APL was generally available only on mainframe computers, and most desktop sized microcomputers such as the Wang 2200 or HP 9800 offered only BASIC. Because SCAMP was the first to emulate APL\1130 performance on a portable, single user computer, PC Magazine in 1983 designated SCAMP a "revolutionary concept" and "the world's first personal computer".PC Magazine, Vol. 2, No. 6, November 1983, ‘'SCAMP: The Missing Link in the PC's Past?‘’ This seminal, single user portable computer now resides in the Smithsonian Institution, Washington, D.C.. Successful demonstrations of the 1973 SCAMP prototype led to the IBM 5100 portable microcomputer launched in 1975 with the ability to be programmed in both APL and BASIC for engineers, analysts, statisticians, and other business problem-solvers. In the late 1960s such a machine would have been nearly as large as two desks and would have weighed about half a ton. Another desktop portable APL machine, the MCM/70, was demonstrated in 1973 and shipped in 1974. It used the Intel 8008 processor. A seminal step in personal computing was the 1973 Xerox Alto, developed at Xerox's Palo Alto Research Center (PARC). It had a graphical user interface (GUI) which later served as inspiration for Apple's Macintosh, and Microsoft's Windows operating system. The Alto was a demonstration project, not commercialized, as the parts were too expensive to be affordable. Also in 1973 Hewlett Packard introduced fully BASIC programmable microcomputers that fit entirely on top of a desk, including a keyboard, a small one-line display, and printer. The Wang 2200 microcomputer of 1973 had a full-size cathode ray tube (CRT) and cassette tape storage. These were generally expensive specialized computers sold for business or scientific uses. The introduction of the microprocessor, a single chip with all the circuitry that formerly occupied large cabinets, led to the proliferation of personal computers after 1975. 1974 saw the introduction of what is considered by many to be the first true "personal computer", the Altair 8800 created by Micro Instrumentation and Telemetry Systems (MITS).Roy A. Allan, A Bibliography of the Personal Computer resource : the Books and Periodical Articles, Allan Publishing - 2006, p. 80''The New York Times Guide to Essential Knowledge, Second Edition: A Desk Reference for the Curious Mind'' (2007). Macmillan, p. 448. Based on the 8-bit Intel 8080 Microprocessor, Wayne Green visited MITS in August 1975 and interviewed Ed Roberts. Article has several paragraphs on the design of the Altair 8800. the Altair is widely recognized as the spark that ignited the microcomputer revolution as the first commercially successful personal computer.Dorf, Richard C., ed. The engineering handbook. CRC Press, 2004. The computer bus designed for the Altair was to become a ''de facto'' standard in the form of the S-100 bus, and the first programming language for the machine was Microsoft's founding product, Altair BASIC. "This announcement 8800 ranks with IBM's announcement of the System/360 a decade earlier as one of the most significant in the history of computing." In 1976, Steve Jobs and Steve Wozniak sold the Apple I computer circuit board, which was fully prepared and contained about 30 chips. The Apple I computer differed from the other kit-style hobby computers of era. At the request of Paul Terrell, owner of the Byte Shop, Jobs and Wozniak were given their first purchase order, for 50 Apple I computers, only if the computers were assembled and tested and not a kit computer. Terrell wanted to have computers to sell to a wide range of users, not just experienced electronics hobbyists who had the soldering skills to assemble a computer kit. The Apple I as delivered was still technically a kit computer, as it did not have a power supply, case, or keyboard when it was delivered to the Byte Shop. The first successfully mass marketed personal computer was the Commodore PET introduced in January 1977. However, it was back-ordered and not available until later in the year. Commodore press release. "The PET computer made its debut recently as the first 100 units were shipped to waiting customers in mid-October 1977." Five months later (June), the Apple II (usually referred to as the "Apple") was introduced, and the TRS-80 from Tandy Corporation / Tandy Radio Shack in summer 1977, delivered in September in a small number. Mass-market ready-assembled computers allowed a wider range of people to use computers, focusing more on software applications and less on development of the processor hardware. , released in 1981]] personal computer produced in 1985–1990 by the Tesla company in the former socialist Czechoslovakia. This computer was produced locally (in Piešťany) due to a lack of foreign currency with which to buy systems from the West.]] During the early 1980s, home computers were further developed for household use, with software for personal productivity, programming and games. They typically could be used with a television already in the home as the computer display, with low-detail blocky graphics and a limited color range, and text about 40 characters wide by 25 characters tall. Sinclair Research, a UK company, produced the ZX Series the ZX80 (1980), ZX81 (1981), and the ZX Spectrum; the latter was introduced in 1982, and totaled 8 million unit sold. Following came the Commodore 64, totaled 17 million units sold. In the same year, the NEC PC-98 was introduced, which was a very popular personal computer that sold in more than 18 million units. Another famous personal computer, the revolutionary Amiga 1000, was unveiled by Commodore on July 23, 1985. The Amiga 1000 featured a multitasking, windowing operating system, color graphics with a 4096-color palette, stereo sound, Motorola 68000 CPU, 256 KB RAM, and 880 KB 3.5-inch disk drive, for US$1,295. Somewhat larger and more expensive systems (for example, running CP/M), or sometimes a home computer with additional interfaces and devices, although still low-cost compared with minicomputers and mainframes, were aimed at office and small business use, typically using "high resolution" monitors capable of at least 80 column text display, and often no graphical or color drawing capability. Workstations were characterized by high-performance processors and graphics displays, with large-capacity local disk storage, networking capability, and running under a multitasking operating system. Eventually, due to the influence of the IBM PC on the personal computer market, personal computers and home computers lost any technical distinction. Business computers acquired color graphics capability and sound, and home computers and game systems users used the same processors and operating systems as office workers. Mass-market computers had graphics capabilities and memory comparable to dedicated workstations of a few years before. Even local area networking, originally a way to allow business computers to share expensive mass storage and peripherals, became a standard feature of personal computers used at home. In 1982 "The Computer" was named Machine of the Year by Time magazine. In the 2010s, several companies such as Hewlett-Packard and Sony sold off their PC and laptop divisions. As a result, the personal computer was declared dead several times during this period. Types Stationary Workstation 1+ from the early 1990s, with a 25 MHz RISC processor]] A workstation is a high-end personal computer designed for technical, mathematical, or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. Workstations are used for tasks such as computer-aided design, drafting and modeling, computation-intensive scientific and engineering calculations, image processing, architectural modeling, and computer graphics for animation and motion picture visual effects. Desktop computer desktop computer]] Prior to the widespread usage of PCs, a computer that could fit on a desk was remarkably small, leading to the "desktop" nomenclature. More recently, the phrase usually indicates a particular style of computer case. Desktop computers come in a variety of styles ranging from large vertical tower cases to small models which can be tucked behind an LCD monitor. In this sense, the term "desktop" refers specifically to a horizontally oriented case, usually intended to have the display screen placed on top to save desk space. Most desktop computers have an external display screen and an external keyboard, which are typically plugged into the computer case. Gaming computer A gaming computer is a standard desktop computer that typically has high-performance hardware, such as a more powerful video card, processor and memory, in order to handle the requirements of demanding video games, which are often simply called "PC games". A number of companies, such as Alienware, manufacture prebuilt gaming computers, and companies such as Razer and Logitech market mice, keyboards and headsets geared toward gamers. All-in-one All-in-one PCs (also known as single-unit PCs) are a subtype of desktop computer that combines the monitor and processor within a single unit. A separate keyboard and mouse are standard input devices, with some monitors including touchscreen capability. The processor and other working components are typically reduced in size relative to standard desktops, located behind the monitor, and configured similarly to laptops. Nettop A subtype of desktops, called nettops, was introduced by Intel in February 2008, characterized by low cost and lean functionality. A similar subtype of laptops (or notebooks) is the netbook, described below. The product line features the new Intel Atom processor, which specifically enables nettops to consume less power and fit into small enclosures. Home theater PC Fusion V2 home theater PC, with a keyboard placed on top of it]] A home theater PC (HTPC) is a convergence device that combines the functions of a personal computer and a digital video recorder. It is connected to a TV set or an appropriately sized computer display, and is often used as a digital photo viewer, music and video player, TV receiver, and digital video recorder. HTPCs are also referred to as media center systems or media servers. The general goal in a HTPC is usually to combine many or all components of a home theater setup into one box. More recently, HTPCs gained the ability to connect to services providing on-demand movies and TV shows. HTPCs can be purchased pre-configured with the required hardware and software needed to add television programming to the PC, or can be cobbled together out of discrete components, what is commonly done with software support from MythTV, Windows Media Center, GB-PVR, SageTV, Famulent or LinuxMCE. Portable Laptop A laptop computer (also called a notebook) is similar to a desktop, but is designed for portability. Usually, all of the hardware and interfaces needed to operate a laptop, such as the graphics card, audio devices or USB ports (previously parallel and serial ports), are built into a single unit. Laptops usually have "clamshell" design, in which the keyboard and computer components are on one panel and a flat display screen on a second panel, which is hinged to the first panel. The laptop is opened for use and closed for transport. Closing the laptop also protects the screen and keyboard during transportation. Laptops have both a power cable that can be plugged in and high-capacity batteries that can power the device, enhancing its portability. Once the battery charge is depleted, it will have to be recharged through a power outlet. In the interests of saving power, weight and space, laptop graphics cards are in many cases integrated into the CPU or chipset and use system RAM, resulting in reduced graphics performance when compared to an equivalent desktop machine. For this reason, desktop computers are usually preferred over laptops for gaming purposes. One of the drawbacks of laptops is that, due to the size and configuration of components, usually relatively little can be done to upgrade the overall computer from its original design or add components. Internal upgrades are either not manufacturer-recommended, can damage the laptop if done with poor care or knowledge, or in some cases impossible, making the desktop PC more modular and upgradable. Desktop PCs typically have a case that has extra empty space inside, where users can install new components. Some internal upgrades to laptops, such as memory and hard disk drive upgrades are often easily performed, while a display or keyboard upgrade is usually difficult or impossible. Just like desktops, laptops also have the same input and output ports for connecting to a wide variety of devices, including external displays, mice, cameras, storage devices and keyboards, which may be attached externally through USB ports and other less common ports such as external video. Laptops are also a little more expensive compared to desktops, as the miniaturized components for laptops themselves are expensive. A subtype of notebooks, called subnotebook, has most of the features of a standard laptop computer, but with smaller physical dimensions. Subnotebooks are larger than hand-held computers, and usually run full versions of desktop or laptop operating systems. Ultra-mobile PCs (UMPC) are usually considered subnotebooks, or more specifically, subnotebook tablet PCs, which are described below. Netbooks are sometimes considered to belong to this category, though they are sometimes separated into a category of their own (see below). Desktop replacement A desktop replacement computer (DTR) is a personal computer that provides the full capabilities of a desktop computer while remaining mobile. Such computers are often actually larger, bulkier laptops. Because of their increased size, this class of computers usually includes more powerful components and a larger display than generally found in smaller portable computers, and can have a relatively limited battery capacity or none at all in some cases. Some use a limited range of desktop components to provide better performance at the expense of battery life. Desktop replacement computers are sometimes called desknotes, as a portmanteau of words "desktop" and "notebook", though the term is also applied to desktop replacement computers in general.Desktop notebooks stake their claim, accessed October 19, 2007 Netbook netbook ]] Netbooks, also called mini notebooks or subnotebooks, are a subgroup of laptops acting as a category of small, lightweight and inexpensive laptop computers suited for general computing tasks and accessing web-based applications. They are often marketed as "companion devices", with an intention to augment other ways in which a user can access computer resources. Walt Mossberg called them a "relatively new category of small, light, minimalist and cheap laptops." By August 2009, CNET called netbooks "nothing more than smaller, cheaper notebooks." Initially, the primary defining characteristic of netbooks was the lack of an optical disc drive, requiring it to be a separate external device. This has become less important as flash memory devices have gradually increased in capacity, replacing the writable optical disc (e.g. CD-RW, DVD-RW) as a transportable storage medium. At their inception in late 2007 as smaller notebooks optimized for low weight and low cost netbooks omitted key features (e.g., the optical drive), featured smaller screens and keyboards, and offered reduced specifications and computing power. Over the course of their evolution, netbooks have ranged in their screen sizes from below five inches to over 13 inches, with weights around ( ). Often significantly less expensive than other laptops, by mid-2009 netbooks had been offered to users "free of charge", with an extended service contract purchase of a cellular data plan. In the short period since their appearance, netbooks have grown in size and features, converging with new smaller and lighter notebooks. By mid-2009, CNET noted that "the specs are so similar that the average shopper would likely be confused as to why one is better than the other," noting "the only conclusion is that there really is no distinction between the devices." Tablet Compaq tablet PC with rotating/removable keyboard]] A tablet is a type of portable PC that de-emphasizes the use of traditional input devices (such as a mouse or keyboard) by using a touchscreen display, which can be controlled using either a stylus pen or finger. Some tablets may use a "hybrid" or "convertible" design, offering a keyboard that can either be removed as an attachment, or a screen that can be rotated and folded directly over top the keyboard. Some tablets may run a traditional PC operating system such as Windows or Linux; Microsoft attempted to enter the tablet market in 2002 with its Microsoft Tablet PC specifications, for tablets and convertible laptops running Windows XP. However, Microsoft's early attempts were overshadowed by the release of Apple's iPad; following in its footsteps, most tablets now run mobile operating systems such as Android and iOS. In response, Microsoft built its Windows 8 operating system to better accommodate these new touch-oriented devices. Many tablet computers have USB ports, to which a keyboard or mouse can be connected. Smartphone Smartphones are practically the same devices as tablet computers, the only differences between them being that smartphones are generally smaller than tablets, always have cellular integration, and (while modern smartphones almost always do) may not always have a slate form factor. Ultra-mobile PC ultra-mobile PC]] The ultra-mobile PC (UMP) is a specification for small-configuration tablet PCs. It was developed as a joint development exercise by Microsoft, Intel and Samsung, among others. Current UMPCs typically feature the Windows XP, Windows Vista, Windows 7, or Linux operating system, and low-voltage Intel Atom or VIA C7-M processors. Pocket PC A pocket PC is a hardware specification for a handheld-sized computer (personal digital assistant, PDA) that runs the Microsoft Windows Mobile operating system. It may have the capability to run an alternative operating system like NetBSD or Linux. Pocket PCs have many of the capabilities of desktop PCs. Numerous applications are available for handhelds adhering to the Microsoft Pocket PC specification, many of which are freeware. Some of these devices also include mobile phone features, actually representing a smartphone. Microsoft-compliant Pocket PCs can also be used with many other add-ons like GPS receivers, barcode readers, RFID readers and cameras. In 2007, with the release of Windows Mobile 6, Microsoft dropped the name Pocket PC in favor of a new naming scheme: devices without an integrated phone are called Windows Mobile Classic instead of Pocket PC, while devices with an integrated phone and a touch screen are called Windows Mobile Professional.New Windows Mobile 6 Devices :: Jun/Jul 2007 Hardware of a personal computer and peripherals (some of which are optional): ]] Computer hardware is a comprehensive term for all physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. The boundary between hardware and software has become blurred, with the existence of firmware that is software "built into" the hardware. For example, a 2010-era LCD display screen contains a small computer inside. Mass-market consumer computers use highly standardized components and so are simple for an end user to assemble into a working system. Most 2010s-era computers only require users to plug in the power supply, monitor, and other cables. A typical desktop computer consists of a computer case (or "tower"), a metal chassis that holds the power supply, motherboard, hard disk drive, and often an optical disc drive. Most towers have empty space where users can add additional components. External devices such as a computer monitor or visual display unit, keyboard, and a pointing device (mouse) are usually found in a personal computer. The motherboard connects all processor, memory and peripheral devices together. The RAM, graphics card and processor are in most cases mounted directly onto the motherboard. The central processing unit (microprocessor chip) plugs into a CPU socket, while the memory modules plug into corresponding memory sockets. Some motherboards have the video display adapter, sound and other peripherals integrated onto the motherboard, while others use expansion slots for graphics cards, network cards, or other I/O devices. The graphics card or sound card may employ a break out box to keep the analog parts away from the electromagnetic radiation inside the computer case. Disk drives, which provide mass storage, are connected to the motherboard with one cable, and to the power supply through another cable. Usually, disk drives are mounted in the same case as the motherboard; expansion chassis are also made for additional disk storage. For large amounts of data, a tape drive can be used or extra hard disks can be put together in an external case. The keyboard and the mouse are external devices plugged into the computer through connectors on an I/O panel on the back of the computer case. The monitor is also connected to the input/output (I/O) panel, either through an onboard port on the motherboard, or a port on the graphics card. Capabilities of the personal computers hardware can sometimes be extended by the addition of expansion cards connected via an expansion bus. Standard peripheral buses often used for adding expansion cards in personal computers include PCI, PCI Express (PCIe), and AGP (a high-speed PCI bus dedicated to graphics adapters, found in older computers). Most modern personal computers have multiple physical PCI Express expansion slots, with some of the having PCI slots as well. Computer case case lying on its side]] A computer case is an enclosure that contains the main components of a computer. They are usually constructed from steel or aluminum combined with plastic, although other materials such as wood and tempered glass have been used for specialized units. Cases are available in different sizes and shapes; the size and shape of a computer case are usually determined by the configuration of the motherboard that it is designed to accommodate since this is the largest and most central component of most computers. The most popular style for desktop computers is ATX, although microATX and similar layouts became very popular for a variety of uses. Companies like Shuttle Inc. and AOpen have popularized small cases, for which FlexATX is the most common motherboard size. In the 1990s, desktop computer cases were larger and taller than 2010-era computer cases. Power supply unit unit with top cover removed]] The power supply unit (PSU) converts general-purpose mains AC electricity to direct current (DC) for the other components of the computer. The rated output capacity of a PSU should usually be about 40% greater than the calculated system power consumption needs to be obtained by adding up all the system components. This protects against overloading the supply, and guards against performance degradation. Power supply capacities range from 250 to 2000 watts for desktop computers. Processor Athlon 64 X2 CPU ]] The central processing unit (CPU) is a part of a computer that executes instructions of a software program. In newer PCs, the CPU contains over a million transistors in one integrated circuit chip called the microprocessor. In most cases, the processor plugs directly into the motherboard. The processor chip may have a heat sink and a fan attached for cooling. IBM PC compatible computers use an x86-compatible microprocessor, manufactured by Intel, AMD, VIA Technologies or Transmeta. Apple Macintosh computers were initially built with the Motorola 680x0 family of processors, then switched to the PowerPC series; in 2006, they switched to x86-compatible processors made by Intel. Motherboard without processor, memory and expansion cards, cables]] The motherboard, also referred to as system board or main board, is the primary circuit board within a personal computer, and other major system components plug directly into it or via a cable. A motherboard contains a microprocessor, the CPU supporting circuitry (mostly integrated circuits) that provide the interface between memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on (often called boot firmware or, in IBM PC compatible computers, a BIOS or UEFI). In many portable and embedded personal computers, the motherboard houses nearly all of the PC's core components. Often a motherboard will also contain one or more peripheral buses and physical connectors for expansion purposes. Sometimes a secondary daughter board is connected to the motherboard to provide further expandability or to satisfy space constraints. Main memory PC-3200 module]] A PC's main memory is a fast primary storage device that is directly accessible by the CPU, and is used to store the currently executing program and immediately needed data. PCs use semiconductor random-access memory (RAM) of various kinds such as DRAM, SDRAM or SRAM as their primary storage. Which exact kind is used depends on cost/performance issues at any particular time. Main memory is much faster than mass storage devices like hard disk drives or optical discs, but is usually volatile, meaning that it does not retain its contents (instructions or data) in the absence of power, and is much more expensive for a given capacity than is most mass storage. As a result, main memory is generally not suitable for long-term or archival data storage. Storage drive 250 GB hard disk drive]] Mass storage devices store programs and data even when the power is off; they do require power to perform read and write functions during usage. Although flash memory has dropped in cost, the prevailing form of mass storage in personal computers is still the hard disk drive. If the mass storage controller provides additional ports for expandability, a PC may also be upgraded by the addition of extra hard disk or optical disc drives. For example, BD-ROMs, DVD-RWs, and various optical disc recorders may all be added by the user to certain PCs. Standard internal storage device connection interfaces are PATA, SATA and SCSI. Solid state drives (SSDs) are a much faster replacement for traditional mechanical hard disk drives but are also more expensive in terms of cost per gigabyte. Solid state drives connect using several connectors, including SATA, M.2, and U.2. Some models use the NVMe protocol, which have vastly improved performance over standard hard disk drives and older SSDs that use the older AHCI protocol. Visual display unit A visual display unit, computer monitor or just display, is a piece of electrical equipment, usually separate from the computer case, which displays visual images without producing a permanent computer record. A display device was usually either a CRT in the 1980s, but by the 2000s, flat panel displays such as a TFT LCD had largely replaced the bulkier, heavier CRT screens. Multi-monitor setups are quite common in the 2010s, as they enable a user to display multiple programs at the same time (e.g., an email inbox and a word processing program). The display unit houses an electronic circuitry that generates its picture from signals received from the computer. Within the computer, either integral to the motherboard or plugged into it as an expansion card, there is pre-processing circuitry to convert the microprocessor's output data to a format compatible with the display unit's circuitry. The images from computer monitors originally contained only text, but as graphical user interfaces emerged and became common, they began to display more images and multimedia content. The term "monitor" is also used, particularly by technicians in broadcasting television, where a picture of the broadcast data is displayed to a highly standardized reference monitor for confidence checking purposes. Video card video card]] The video card — otherwise called a graphics card, graphics adapter or video adapter — processes the graphics output from the motherboard and transmits it to the display. It is an essential part of modern multimedia-enriched computing. Graphics circuitry may be integrated with the motherboard, or may be on cards istalled in PCI, AGP, or PCI Express slots. When the IBM PC was introduced, most existing business-oriented personal computers used text-only display adapters and had no graphics capability. Home computers at that time had graphics compatible with television signals, but with low resolution owing to the limited memory available to the eight-bit processors available at the time. Keyboard IBM computer keyboard from the early 1980s. Commonly called the "Clicky Keyboard" due to its buckling spring key spring design, which gives the keyboard its iconic 'click' sound with each keystroke.]] A keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices used for inputting text. In most cases, they contain an array of keys specifically organized with the corresponding letters, numbers, and functions printed or engraved on the button. They are generally designed around an operators language, and many different versions for different languages exist. In English, the most common layout is the QWERTY layout, which was originally used in typewriters. They have evolved over time, and have been modified for use in computers with the addition of function keys, number keys, arrow keys, and keys specific to an operating system. Often, specific functions can be achieved by pressing multiple keys at once or in succession, such as inputting characters with accents or opening a task manager. Programs use keyboard shortcuts very differently and all use different keyboard shortcuts for different program specific operations, such as refreshing a web page in a web browser or selecting all text in a word processor. In addition to the alphabetic keys found on a typewriter, computer keyboards typically have a numeric keyboard and a row of function keys and special keys, such as CTRL, ALT, DEL and Esc Many keyboards include LED lights under the keys that increase the visibility of the letters or symbols in dark environments. Mouse A computer mouse is a small handheld device that users hold and slide across a flat surface, pointing at various elements of a graphical user interface with an on-screen cursor, and selecting and moving objects using the mouse buttons. Mice may be plugged into a dedicated mouse socket, or a USB port, or, may be connected wirelessly. Mice include one or more buttons to allow a user to signal the computer to carry out some operation, such as selecting an item from a menu of choices on the screen. A mouse may have a scroll wheel, to allow users to move the displayed image. The scroll wheel can also be pressed down, and used as a third button. Some mouse wheels may be tilted from side to side to allow sideways scrolling. Different programs make use of these functions differently, and may scroll horizontally by default with the scroll wheel, open different menus with different buttons, etc. These functions may be also user-defined through software utilities. Mechanical mice used a ball, which drove pulse generators to detect movement along "north-south" or "east-west" axies. Optical mice use a special mouse pad with a printed grid to allow detection of motion, or else use an imaging chip that allows detection of motion on almost any opaque surface. Other components All computers require either fixed or removable storage for their operating system, programs and user-generated material. Early home computers used compact audio cassettes for file storage; these were at the time a very low cost storage solution, but were displaced by floppy disk drives when manufacturing costs dropped, by the mid-1980s. Initially, the 5.25-inch and 3.5-inch floppy drives were the principal forms of removable storage for backup of user files and distribution of software. As memory sizes increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable media were introduced but never became as prevalent as the floppy drive. By the late 1990s, the optical drive, in CD and later DVD and Blu-ray Disc forms, became the main method for software distribution, and writeable media provided means for data backup and file interchange. As a result, floppy drives became uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier.The NeXT computer introduced in 1988 did not include a floppy drive, which at the time was unusual. A second generation of tape recorders was provided when videocassette recorders were pressed into service as backup media for larger disk drives. All these systems were less reliable and slower than purpose-built magnetic tape drives. Such tape drives were uncommon in consumer-type personal computers but were a necessity in business or industrial use. Interchange of data such as photographs from digital cameras is greatly expedited by installation of a card reader, which is often compatible with several forms of flash memory devices. It is usually faster and more convenient to move large amounts of data by removing the card from the mobile device, instead of communicating with the mobile device through a USB interface. A USB flash drive performs much of the data transfer and backup functions formerly done with floppy drives, Zip disks and other devices. Mainstream operating systems for personal computers provide built-in support for USB flash drives, allowing interchange even between computers with different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined with low cost and high capacity, have made USB flash drives a popular and useful accessory for any personal computer user. The operating system can be located on any storage, but is typically installed on a hard disk or solid-state drive. A Live CD represents the concept of running an operating system directly from a CD. While this is slow compared to storing the operating system on a hard disk drive, it is typically used for installation of operating systems, demonstrations, system recovery, or other special purposes. Large flash memory is currently more expensive than hard disk drives of similar size (as of mid-2014) but are starting to appear in laptop computers because of their low weight, small size and low power requirements. Computer communications involve internal modem cards, modems, network adapter cards, and routers. Common peripherals and adapter cards include headsets, joysticks, microphones, printers, scanners, sound adapter cards (as a separate card rather than located on the motherboard), speakers and webcams. Software software]] Computer software is any kind of computer program, procedure, or documentation that performs some task on a computer system. The term includes application software such as word processors that perform productive tasks for users, system software such as operating systems that interface with computer hardware to provide the necessary services for application software, and middleware that controls and co-ordinates distributed systems. Software applications are common for word processing, Internet browsing, Internet faxing, e-mail and other digital messaging, multimedia playback, playing of computer game, and computer programming. The user may have significant knowledge of the operating environment and application programs, but is not necessarily interested in programming nor even able to write programs for the computer. Therefore, most software written primarily for personal computers tends to be designed with simplicity of use, or "user-friendliness" in mind. However, the software industry continuously provide a wide range of new products for use in personal computers, targeted at both the expert and the non-expert user. Operating system An operating system (OS) manages computer resources and provides programmers with an interface used to access those resources. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. An operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating computer networking, and managing files. Common contemporary desktop operating systems are Microsoft Windows, macOS, Linux, Solaris and FreeBSD. Windows, macOS, and Linux all have server and personal variants. With the exception of Microsoft Windows, the designs of each of them were inspired by or directly inherited from the Unix operating system, which was developed at Bell Labs beginning in the late 1960s and spawned the development of numerous free and proprietary operating systems. Microsoft Windows Microsoft Windows is the collective brand name of several operating systems made by Microsoft which, as of 2015, are installed on PCs built by HP, Dell and Lenovo, the three remaining high volume manufacturers. Microsoft first introduced an operating environment named Windows in November 1985, as an add-on to MS-DOS and in response to the growing interest in graphical user interfaces (GUIs) generated by Apple's 1984 introduction of the Macintosh. , the most recent client and server version of Windows are Windows 10 and Windows Server 2016. macOS macOS (formerly OS X) is a line of operating systems developed, marketed and sold by Apple Inc. macOS is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. macOS is a Unix-based graphical operating system, and Snow Leopard, Leopard, Lion, Mountain Lion, Mavericks, Yosemite, El Capitan and Sierra are its version codenames. The most recent version of macOS is codenamed macOS High Sierra. Linux running KDE Plasma Workspaces 4 ]] Linux is a family of Unix-like computer operating systems. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone. The name "Linux" refers to the Linux kernel, started in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU operating system, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux. Known for its use in servers, with the LAMP application stack as one of prominent examples, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, Canonical Ltd. and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, netbooks, supercomputers, video game systems such as the Steam Machine or PlayStation 3 (until this option was removed remotely by Sony in 2010 ), several arcade games, and embedded devices such as mobile phones, portable media players, routers, and stage lighting systems. Applications , which is a raster graphics editor.]] Generally, a computer user uses application software to carry out a specific task. System software supports applications and provides common services such as memory management, network connectivity and device drivers, all of which may be used by applications but are not directly of interest to the end user. A simplified analogy in the world of hardware would be the relationship of an electric light bulb (an application) to an electric power generation plant (a system): the power plant merely generates electricity, not itself of any real use until harnessed to an application like the electric light that performs a service that benefits the user. Typical examples of software applications are word processors, spreadsheets, and media players. Multiple applications bundled together as a package are sometimes referred to as an application suite. Microsoft Office and LibreOffice, which bundle together a word processor, a spreadsheet, and several other discrete applications, are typical examples. The separate applications in a suite usually have a user interface that has some commonality making it easier for the user to learn and use each application. Often, they may have some capability to interact with each other in ways beneficial to the user; for example, a spreadsheet might be able to be embedded in a word processor document even though it had been created in the separate spreadsheet application. End-user development tailors systems to meet the user's specific needs. User-written software include spreadsheet templates, word processor macros, scientific simulations, graphics and animation scripts; even email filters are a kind of user software. Users create this software themselves and often overlook how important it is. Gaming PC gaming is popular among the high-end PC market. According to an April 2014 market analysis, Gaming platforms like Steam (software), Uplay, Origin, and GOG.com (as well as competitive e Sports titles like League of Legends) are largely responsible for PC systems overtaking console revenue in 2013. Sales Market share In 2001, 125 million personal computers were shipped in comparison to 48,000 in 1977. More than 500 million personal computers were in use in 2002 and one billion personal computers had been sold worldwide from the mid-1970s up to this time. Of the latter figure, 75% were professional or work related, while the rest were sold for personal or home use. About 81.5% of personal computers shipped had been desktop computers, 16.4% laptops and 2.1% servers. The United States had received 38.8% (394 million) of the computers shipped, Europe 25% and 11.7% had gone to the Asia-Pacific region, the fastest-growing market as of 2002. The second billion was expected to be sold by 2008. Almost half of all households in Western Europe had a personal computer and a computer could be found in 40% of homes in United Kingdom, compared with only 13% in 1985. The global personal computer shipments were 350.9 million units in 2010,Global PC shipments grew 13.8 percent in 2010 – Gartner study, Jan 13, 2011, retrieved at September 12, 2011 308.3 million units in 2009Laptop Sales Soaring Amid Wider PC Growth: Gartner, May 27, 2010, Andy Patrizio, earthweb.com, retrieved at September 12, 2011 and 302.2 million units in 2008.Worldwide PC Shipments in 2008, March 16, 2009, ZDNet, retrieved at September 12, 2011PC Sales Up for 2008, but Barely, January 14, 2009, Andy Patrizio, internetnews.com, retrieved at September 12, 2011 The shipments were 264 million units in the year 2007, according to iSuppli, up 11.2% from 239 million in 2006. In 2004, the global shipments were 183 million units, an 11.6% increase over 2003. In 2003, 152.6 million computers were shipped, at an estimated value of $175 billion. In 2002, 136.7 million PCs were shipped, at an estimated value of $175 billion. In 2000, 140.2 million personal computers were shipped, at an estimated value of $226 billion. Worldwide shipments of personal computers surpassed the 100-million mark in 1999, growing to 113.5 million units from 93.3 million units in 1998. In 1999, Asia had 14.1 million units shipped. As of June 2008, the number of personal computers in use worldwide hit one billion, while another billion is expected to be reached by 2014. Mature markets like the United States, Western Europe and Japan accounted for 58% of the worldwide installed PCs. The emerging markets were expected to double their installed PCs by 2012 and to take 70% of the second billion PCs. About 180 million computers (16% of the existing installed base) were expected to be replaced and 35 million to be dumped into landfill in 2008. The whole installed base grew 12% annually. Based on International Data Corporation (IDC) data for Q2 2011, for the first time China surpassed US in PC shipments by 18.5 million and 17.7 million respectively. This trend reflects the rising of emerging markets as well as the relative stagnation of mature regions. In the developed world, there has been a vendor tradition to keep adding functions to maintain high prices of personal computers. However, since the introduction of the One Laptop per Child foundation and its low-cost XO-1 laptop, the computing industry started to pursue the price too. Although introduced only one year earlier, there were 14 million netbooks sold in 2008. Besides the regular computer manufacturers, companies making especially rugged versions of computers have sprung up, offering alternatives for people operating their machines in extreme weather or environments. In 2011, Deloitte consulting firm predicted that, smartphones and tablet computers as computing devices would surpass the PCs salesTablets, smartphones to outsell PCs https://news.yahoo.com/s/afp/20110210/tc_afp/itinternettelecomequipmentmobileconsumerproduct (as has happened since 2012). As of 2013, worldwide sales of PCs had begun to fall as many consumers moved to tablets and smartphones for gifts and personal use. Sales of 90.3 million units in the 4th quarter of 2012 represented a 4.9% decline from sales in the 4th quarter of 2011. Global PC sales fell sharply in the first quarter of 2013, according to IDC data. The 14% year-over-year decline was the largest on record since the firm began tracking in 1994, and double what analysts had been expecting. The decline of Q2 2013 PC shipments marked the fifth straight quarter of falling sales. "This is horrific news for PCs," remarked an analyst. "It's all about mobile computing now. We have definitely reached the tipping point." Data from Gartner Inc. showed a similar decline for the same time period. China's Lenovo Group bucked the general trend as strong sales to first time buyers in the developing world allowed the company's sales to stay flat overall. Windows 8, which was designed to look similar to tablet/smartphone software, was cited as a contributing factor in the decline of new PC sales. "Unfortunately, it seems clear that the Windows 8 launch not only didn’t provide a positive boost to the PC market, but appears to have slowed the market," said IDC Vice President Bob O’Donnell. In August 2013, Credit Suisse published research findings that attributed around 75% of the operating profit share of the PC industry to Microsoft (operating system) and Intel (semiconductors). According to IDC, in 2013 PC shipments dropped by 9.8% as the greatest drop-ever in line with consumers trends to use mobile devices. Average selling price Selling prices of personal computers steadily declined due to lower costs of production and manufacture, while the capabilities of computers increased. In 1975, an Altair kit sold for only around US$400, but required customers to solder components into circuit boards; peripherals required to interact with the system in alphanumeric form instead of blinking lights would add another $2,000, and the resultant system was only of use to hobbyists.Marvin B. Sussman Personal Computers and the Family Routledge, 1985 , p. 90. At their introduction in 1981, the US$1,795 price of the Osborne 1 and its competitor Kaypro was considered an attractive price point; these systems had text-only displays and only floppy disks for storage. By 1982, Michael Dell observed that a personal computer system selling at retail for about $3,000 US was made of components that cost the dealer about $600; typical gross margin on a computer unit was around $1,000.Kateri M. Drexler Icons of business: an encyclopedia of mavericks, movers, and shakers, Volume 1, Greenwood Publishing Group, 2007, , p. 102 The total value of personal computer purchases in the US in 1983 was about $4 billion, comparable to total sales of pet food. By late 1998, the average selling price of personal computer systems in the United States had dropped below $1,000.[http://www.pcworld.com/article/9150/average_pc_price_drops_below_1000.html Nancy Weil, Average PC Price drops below $1000, PC World December 1998. Retrieved November 17, 2010.] For Microsoft Windows systems, the average selling price (ASP) showed a decline in 2008/2009, possibly due to low-cost netbooks, drawing $569 for desktop computers and $689 for laptops at U.S. retail in August 2008. In 2009, ASP had further fallen to $533 for desktops and to $602 for notebooks by January and to $540 and $560 in February. According to research firm NPD, the average selling price of all Windows portable PCs has fallen from $659 in October 2008 to $519 in October 2009. Environmental impact External costs of environmental impact are not fully included in the selling price of personal computers. This impact differs between desktop computers and laptops. Personal computers have become a large contributor to the 50 million tons of discarded electronic waste that is being generated annually, according to the United Nations Environment Programme. To address the electronic waste issue affecting developing countries and the environment, extended producer responsibility (EPR) acts have been implemented in various countries and states. Organizations, such as the Silicon Valley Toxics Coalition, Basel Action Network, Toxics Link India, SCOPE, and Greenpeace have contributed to these efforts. In the absence of comprehensive national legislation or regulation on the export and import of electronic waste, the Silicon Valley Toxics Coalition and BAN (Basel Action Network) teamed up with 32 electronic recyclers in the US and Canada to create an e-steward program for the orderly disposal of manufacturers' and customers' electronic waste. The Silicon Valley Toxics Coalition founded the Electronics TakeBack Coalition, a coalition that advocates for the production of environmentally friendly products. The TakeBack Coalition works with policy makers, recyclers, and smart businesses to get manufacturers to take full responsibility of their products. There are organizations opposing EPR regulation, such as the Reason Foundation. They see flaws in two principal tenets of EPR: First EPR relies on the idea that if the manufacturers have to pay for environmental harm, they will adapt their practices. Second EPR assumes the current design practices are environmentally inefficient. The Reason Foundation claims that manufacturers naturally move toward reduced material and energy use. See also * Computer virus * Desktop replacement computer * e-waste * Information and communication technologies for development * List of computer system manufacturers * Market share of personal computer vendors * Personal Computer Museum * Pocket-sized palmtop handheld computing device * Portable computer * Public computer * Quiet PC * List of home computers Notes References Further reading * Accidental Empires: How the boys of Silicon Valley make their millions, battle foreign competition, and still can't get a date, Robert X. Cringely, Addison-Wesley Publishing, (1992), * PC Magazine, Vol. 2, No. 6, November 1983, ‘'SCAMP: The Missing Link in the PC's Past?‘’ External links * How Stuff Works pages: ** Dissecting a PC ** How PCs Work ** How to Upgrade Your Computer ** How to Build a Computer Category:American inventions Category:Classes of computers Category:Office equipment Category:Personal computers